The rendered image differs from its svg.

[SamEr32]

I'm trying to render the grandient svg but the result is quite different with oringal svg. I don't understand why the difference happens here and is there any way to fix that?
This is the svg.

This is the png.

[L483]

The individual layers of the generated SVG are not fully opaque. Displaying it inside an application with a grey default background and generating a PNG with a white background will appear differently. To see the effect yourself, place a fully opaque, colored square as the bottom-most layer in a generated SVG, then change the square's color.